Our interest continues to lie in the clinical, and genetic evaluation of families with an inherited predisposition to renal carcinoma.Genotype-phenotype correlations in the Birt-Hogg-Dub syndrome We evaluated 63 families affected with the Birt-Hogg-Dub syndrome for germline mutations in the BHD gene, and for clinical manifestations of the disease. We detected germline mutations in 52/63 (83%) of the BHD families. A mutation "hot spot" was located in a cytosine homonucleotide tract. Deletion or addition of a single nucleotide at this cytosine homonucleotide tract accounted for about half of the germline mutations in the BHD gene. All germline mutations that we detected were predicted to truncate the BHD protein. No missense mutations were detected. We looked for correlations between specific germline BHD mutations and the penetrance of renal cell carcinoma. Patients with germline mutations at the cytosine homonucleotide tract comprised the largest group of patients with identical mutations. There was a difference in the frequency of renal cell carcinoma in patients with a C insertion compared to a C deletion at the cytosine homonucleotide tract. Renal tumors were more common in men compared to women and usually occurred after age 40.Biochemical studies of the Birt-Hogg-Dub syndrome protein, folliculin No homology to other human proteins was found although folliculin was conserved across species. This fact prompted us to perform an in depth study to determine the normal function of folliculin. As a first step, we measured the expression of BHD mRNA in normal and neoplastic tissues. There was a wide expression pattern in many tissues including skin, lung and kidney. Folliculin was located in the cytoplasm by cell fractionation and fluorescence studies. A folliculin-binding protein was identified by immunoprecipitation and by mass spectrometry.The BHD gene is a tumor suppressor Our collaborators, Cathy Vocke and Marston Linehan, have detected consistent inactivation, by point mutation, of the wild-type copy of the BHD gene in renal tumors from patients affected with the Birt-Hoog- Dub syndrome. This data provides strong support for the idea that the BHD gene is a tumor suppressor.Studies of families affected with Familial Renal Carcinoma We have recruited patients/families with two or more individuals affected with renal carcinoma by a mailing to urologists and medical oncologists. Field trips have been made to several of these families to obtain informed consent, clinical information and a blood sample. We are working together with Joan Bailey-Wilson, statistical geneticist in our studies of these families. We are determining whether Familial Renal Carcinoma is homogeneous in terms of renal tumor pathology and what the empiric risk for renal tumor development is in at-risk family members. We are also testing whether renal tumors from members of FRC families have somatic VHL mutations, and evaluating the distribution of renal carcinoma risk factors.Identification of families affected with Hereditary Leiomyoma Renal Cell Carcinoma Evaluation of the Familial Renal Carcinoma families requires removing families with known forms of inherited renal cell carcinoma. We found several families who had germline mutations in the fumarate hydratase gene among our panel of families considered to have Familial Renal Carcinoma.Studies of case-control populations affected with renal carcinoma We are planning collaborative studies on case-control populations affected with renal carcinoma with Dr. Lee Moore and Dr. Wong Ho Chow. These studies will include testing of renal tumors for somatic VHL mutationsCollaborative studies with Steven Hou on homologs of folliculin We are evaluating the normal function of the Drosophila homolog of the human BHD gene and the normal function of the folliculin-binding proteins.